Devices and systems having transducers which transduce electrical energy to and from undulation pressure waves such as audio, acoustical, sonic and ultrasonic pressure waves, have existed for some time. Such transducers may include crystal, piezoelectric, magnetostrictive, inductive, vibrating, diaphragm, audio, acoustic, sonic, subsonic and ultrasonic transducers, among many other exemplar types of transducers. In a forward direction, the transducers are coupled to sources of electrical energy having frequencies of respective energizing signals at the resonant frequencies of the transducers for efficient transfer of energy from the electrical energy sources to the transducers then imparting energy in the form of the oscillating undulating pressure waves to loads coupled to the transducers. In a reverse direction, the transducers receive energy of undulating pressure waves from sources of undulating pressure waves and transduce the energy of those undulating pressure waves into electrical energy delivered to loads of electrical energy.
U.S. Pat. No. 3,958,559 entitled Ultrasonic Transducer teaches an ultrasound pulse echo imaging system using plano concave lens of elliptical shape positioned in front of the transducer for producing an extremely narrow ultrasonic beam and providing a large aperture to maximize ultrasound power output from the transducer and capture angle of reflected echoes. The transducer both sends through electrical excitation and receives ultrasonic wave beams generating electrical output signals. The transducer is a conventional flat disc transducer producing an essentially collimated beam of ultrasound of frontal parallel pressure waves but having an ellipsoidal plano concave leans disposed in the front of the transducer though bonding or positioning using a coupling medium. The produced ultrasonic wave intensity may have a uniform, Gaussian, or some other desired distribution. Other types of transducers may be shaped to include a transmitting receiving curved surface for focused transmission and collective reception of the ultrasonic waves. Various types of transmitting and receiving transducers having coupled lens or curved surfaces for focused transmission and collective reception of ultrasonic waves are well known by those skilled in the art of ultrasonic transducer designs.
U.S. Pat. No. 4,368,410 entitled Ultrasound Therapy Device teaches maintaining constant electrical energizing power to a transducer regardless of the load on the transducer using an analog servo feedback circuit. The device may be operated to emit an ultrasonic frequency and driven by continuous wave signals, or pulse mode signals where the pulse period and duration are selectable using operator switches. The pulse range may be between ten and five hundred microseconds. Negative feedback signals representing current and voltage drawn by the transducer are supplied to an analog multiplier where the actual power delivered to the transducer is calculated and used to maintain the power delivered to the transducer. Comparators are used to supply error signals for open and closed circuit conditions to prevent loss of coupling or overheating of the transducer. These types of closed loop control and sensing systems, methods and implementing devices are well known by those skilled in the art of transducer device and system design.
U.S. Pat. No. 4,966,131 entitled Ultrasound Power Generating System with Sample Data Frequency Control teaches the use of a disk shaped crystal transducer actuated by an electrical power source having a control frequency for the efficient coupling of electrical energy into acoustic energy injected into a human body. The system includes the crystal transducer having excitation electrodes and radio frequency (RF) power amplifiers for supplying electrical power to the transducer. The system includes a single chip microprocessor having analog to digital converters, digital to analog converters, input-output communication means, on board random access memory (RAM) and read only memory (ROM) for operational sensing and control of electrical circuits including an RF signal sensor and a voltage controlled oscillator for controlling the excitation frequency to efficiently deliver electrical power to the transducer then providing desired acoustic energy to a human load. These types of microprocessor and connected circuit designs for electrically driving ultrasonic transducers are well known by those skilled in the art of transducer device and system designs.
U.S. Pat. No. 5,396,888 entitled Non Contact Tonometer and Method of Using Ultrasonic Beams teaches an ultrasonic transducer directing an ultrasonic beam which is detected by an ultrasonic or optical means. An ultrasonic beam is used for ranging measurements. The ultrasonic transducer may be activated by continuous wave of pulse mode signals using electronic feed back control. High ultrasonic frequencies between 100.0 KHz and 1.0 MHz are used to energize a transducer generating and projecting the directed ultrasonic beam. The ultrasonic beam can be modulated, directed and focused by conventional means. The ultrasonic power level can be modulated at high frequency to enable phase sensitive demodulation for detection. High bandwidth servo loops can control the intensity of the ultrasonic beam. The ultrasonic beams produce a pressure field with a Gaussian profile. The transducer may be a piezoelectric crystal, magnetostrictive element or a vibrating diaphragm, among others.
This patented transducer system comprises a plurality of coupled transducers, a primary transducer for transmitting the directed ultrasonic beam and secondary transducers for detecting the effect of the primary directed beam communicated at least in part through a coupling medium. The primary transducer is activated by an oscillator producing an amplitude modulation of an ultrasonic frequency signal. One secondary transducer detects a reflected ultrasonic beam indicating the amount of indentation effect of the primary ultrasonic beam on human eye tissue reflecting the transmitted beam. Another secondary ultrasonic transducer is for detecting and measuring the power transmitted and for controlling the amount of power transmitted by the primary transducer. Another secondary ultrasonic ranging transducer is colocated with the primary transducers and is used for detecting the transmitted beam for aligning the primary transducer with the eye load. The secondary transducer for measuring the indentation can be switched from either transmitting or receiving the directed ultrasonic beam. Transducer input and output signals can be modulated and demodulated for signal transmission and phase detection using conventional mixers and phase detectors. Systems and devices for generating, directing and focusing a primary transducer beam through a coupling medium for subsequent detection by a plurality of secondary transducers are well known by those skilled in the art of ultrasonic transducer device and system design.
Those skilled in the art of transducer devices and systems are well adept at configuring specific transducers and electronic components for generating undulating pressure waves transmitted into and or received through a coupling medium for detecting information about the medium or its contents. However, those transducer devices and systems disadvantageously rely only on the sensing of the acoustic transmitting and reflecting properties of the medium and or its contents to obtain information about the system.
There are many applications that sense critical operating parameters of a component in which it is exceedingly undesirable to connect electrical wires between the power supplies and the sensors, actuators, controllers, processors, and transmitters and receivers.
Continuing progress in Micro Electro Mechanical Systems (MEMS) has led to the development of advanced, miniaturized, multi-functional systems which provide improved capabilities for sensing, monitoring and control of various parameters and functions at very low power to enhance the health, safety, and reliability of current generation spacecraft and launch vehicles, as well as on newly emerging concepts for miniature spacecraft. Such devices are also useful in terrestrial applications such as motor vehicles and structures. Current MEMS devices often take advantage of manufacturing technologies developed for microelectronics, along with subscaled applications of macroscopic devices such as valves, pumps, or power systems. Typical MEMS systems disadvantageously require the use of external power supplies and data processors for controlling the operation of systems and sensing information about systems. Many applications of micro devices, particularly micro sensors, require that the devices be wireless. This has led to devices having limited usefulness and lifetime due to the limited capacity of on board batteries. These and other disadvantages are solved or reduced using the invention.